CDMA receiver, path search method and program

Abstract

To perform path search processing by means of a smaller amount of calculation and less power consumption, region index calculator 29 decides, for each region resulting from subdividing the delay profile measurement range, whether or not it is a region in which there is a peak, and supplies the results of these decisions as index information. On the basis of this index information, region designation calculator 27 outputs information indicative of whether or not a given region is a region in which a path is present. On the basis of the information from region designation calculator 27, data classifier 24 classifies data, after analogue-to-digital conversion, into data of regions in which there is a path and data of regions in which there is no path. Data integrator 25 integrates the data of the plurality of regions in which no path is present, making it into data of a single imaginary region, and data combiner 26 combines the data of the regions integrated by data integrator 25, with the data of the regions in which there is a path. Delay profile measuring unit 33 forms a delay profile by calculating the correlation power of the combined data at each of a plurality of delays.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a CDMA receiver, and in particular to a method of searching for paths by calculating the delay profile at prescribed intervals, this delay profile showing the power distribution of the received signal as a function of delay.[0003]2. Description of Related Art[0004]In mobile communications, the spread in the propagation path lengths of the signal received in a multipath environment means that there are multiple waves having different propagation delays. A feature of direct sequence code division multiple access (DS-CDMA) is that it is capable of separating and extracting these multiple waves in the form of a so-called “delay profile”, by using a wide-bandwidth spreading code to spread the narrowband data. It is well known that in DS-CDMA communications a diversity effect can be obtained and receiving characteristics improved by rake combining this plurality of multipath signals with diffe...

AI Technical Summary

Benefits of technology

[0009]It is an object of the present invention to provide a CDMA receiver and a path search method capable of performing, with a smaller amount of calculation and power consumption, the path search processing for discovering valid paths from a delay profile that has been obtained.

[0016]This invention is designed to split the delay profile measurement range into a plurality of regions; to classify the split regions into those in which a path is present and those in which a path is not present; and to calculate the delay profile by calculating, in the case of the data of regions in which a path is present, the correlation power in each region; and, in the case of the data of regions in which a path is not present, calculating the correlation power after these data have been integrated as the data of a single imaginary region. Accordingly, this invention facilitates a reduction in the amount of data required to obtain the correlation power, and enables path search processing, for discovering valid paths from a delay profile that has been obtained, to be carried out with a smaller amount of calculation and power consumption.

[0022]This invention is designed to split the delay profile measurement range into a plurality of regions; to classify the split regions into those in which a path is present and those in which a path is not present; and to calculate the delay profile in the case of data of regions in which a path is present, by using a conventional correlation code to calculate the correlation power in each region; and, in the case of regions in which a path is not present, by using a correlation code that has been combined on the basis of the delay differences among these plurality of regions in which a path is not present, to calculate the correlation power, finding, by means of a single correlation power calculation, the value obtained by integrating the correlation powers of the plurality of regions in which a path is not present. Accordingly, because this invention facilitates a reduction in the amount of computation required to calculate the correlation power, it enables path search processing, for discovering valid paths from a delay profile that has been obtained, to be carried out with a smaller amount of calculation and power consumption.

Problems solved by technology

However, because the relative position of a mobile station changes relative to a base station, the radio wave transmission environment around the mobile station varies and hence the delay profile also changes.

For this reason, the delay profile measured by the multipath searcher also varies, which results in variation in the delay associated with a path to be rake combined.

However, because there is generally a large amount of data and always a considerable amount of calculation required to obtain this correlation, a conventional path search method that performs the same correlation computation for all timings within the delay profile measurement range has inevitably taken considerable time to perform the processing required to detect paths from the delay profile, and its implementation has been associated with high power consumption.

A problem encountered with the conventional CDMA receiver described above is that because an enormous amount of computation is required in the path search processing for discovering valid paths from a delay profile that has been obtained, both the amount of calculation and the power consumption are large.

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